Throw like a girl? With some practice, you can do better.

Luckily, it’s not difficult to avoid situations in which throwing is required, and I’ve managed to do it successfully my entire adult life. Except that one time.

A decade or so ago, in New York, a ball came flying over an 18-foot schoolyard fence just as I was passing by. There was no one I could hand it off to, and a gaggle of fifth-graders was waiting for me to toss it back. I had so little faith in my overarm throwing that I had to go underhand. The squeal of brakes was my first indication that the ball had ended up behind me, in the middle of Columbus Avenue. The best I can say about this incident is that nobody got hurt.

I know I’m not the only woman with that kind of story. As much as the expression grates, girls do, in general, throw like girls.

Janet Hyde, a professor of psychology and women’s studies at the University of Wisconsin at Madison, has studied the gender gap across a broad spectrum of skills. She believes that men and women aren’t as different as they are often portrayed, and she has mined data on social, psychological, communication and physical traits, skills and behaviors to quantify the gap. After looking at 46 meta-analyses, Hyde found what she defined as a “very large” difference in only two skills: throwing velocity and throwing distance.

The throwing gap has been researched for more than half a century, and the results have been consistent. According to Jerry Thomas, dean of the College of Education at the University of North Texas in Denton, who did the throwing research Hyde cites in her paper, “The overhand throwing gap, beginning at 4 years of age, is three times the difference of any other motor task, and it just gets bigger across age. By 18, there’s hardly any overlap in the distribution: Nearly every boy by age 15 throws better than the best girl.”

Around the world, at all ages, boys throw better — a lot better — than girls. Studies of overhand ball throwing across different cultures have found that pre-pubescent girls throw 51 to 69 percent of the distance that boys do, at 51 to 78 percent of the velocity. As they get older, the differences increase; one U.S. study found that girls age 14 to 18 threw only 39 percent as far as boys (an average of about 75 feet vs. about 192 feet). The question is why.

Since boys generally learn to throw young and do more throwing than girls do, it would make sense that they’re better at it, and Thomas acknowledges the nurture component. “The gap is much larger than it should be, and it would be smaller if girls got more practice,” he says.

To try to distinguish nature from nurture, Thomas studied aboriginal Australian children, who grow up in a culture where both men and women hunt, and both sexes throw from childhood. “Our hypothesis was that [the aboriginal] girls would be better throwers and not as different from the boys as in European, Chinese, Australian and all the U.S. cultures.”

The data bore him out. Aboriginal girls threw tennis balls at 78.3 percent of the velocity of boys — closer to boys than in most other cultures, but still significantly slower. (Throwing distance wasn’t measured.)

Size and strength undoubtedly also play a role, but girls and boys are about the same size as children, when there is a significant gap in overhand throwing skill. The gap widens at puberty, when the advantages of size and strength kick in.

Like a dart, not a ball

To understand why a girl “throws like a girl,” it’s necessary to define just what throwing like a girl is. According to Thomas, a girl throwing overhand looks more like she’s throwing a dart than a ball. It’s a slow, weak, forearm motion, with a short step on the same side as the throwing hand. A boy’s throw, by contrast, involves the entire body. Thomas describes a skillful overhand throw as an uncoiling in three phases: step (with the foot opposite the throwing hand), rotate (with hips first, then shoulders) and whip (with the arm and hand).

Girls don’t do any of those three steps as successfully as boys, but Thomas zeroes in on one aspect in particular: the rotation.

The power in an overhand throw — and in a golf swing, a tennis serve or a baseball swing — comes from the separate turning of hips and shoulders. The hips rotate forward and the body opens, and then the shoulders snap around. Women tend to rotate their hips and shoulders together, and even expert women throwers don’t get the differential that men get. “The one-piece rotation is the biggest difference,” says Thomas. “It keeps women from creating speed at the hand.” Even when women learn to rotate hips and shoulders separately, they don’t do it as fast as men.

There doesn’t appear to be a muscular or structural reason for the difference.

“Men have wider shoulders, which translates to higher velocity at ball release. They’re bigger and stronger, and you could argue they can rotate their body faster, but the women have less mass to rotate,” Thomas says. The difference, he suspects, isn’t in the arm or the torso or the shoulder. “I’d bet my bottom dollar there’s something neurological. It’s the nervous system.”

This explanation, while not explicitly provable, would make evolutionary sense. “Men threw rocks, and, if you could throw well, you got the women,” Thomas points out. “Women did the gathering, and often brought a baby with them. People have speculated that [one-piece] rotation came from women having to throw while holding a baby.”

Thomas points out that a biological explanation isn’t palatable to everyone. “If you say something is biological.” he says, “people think you should just give up and go home.” Janet Hyde agrees: “The more we argue for gender differences, the more we feed people’s stereotypes. A belief in large gender differences is incompatible with equal opportunity.” Still, Hyde readily acknowledges that there are some biological differences, and throwing is one of them.

Thomas doesn’t want to give up and go home. “People don’t like to talk about it because girls will give up, but perhaps if we talk about it, girls can learn. And they can learn.”

Taking a lesson

Jenny Allard, coach of the Harvard women’s softball team, is doing the teaching. “Overhand throwing is the most undertaught skill in softball,” she says. “Girls tend to keep their limbs close to their body, and not rotate at all, If they do rotate, they rotate their entire body.” She sees the problem even at the elite level. “I saw a potential recruit who was fast as lightning, and a great hitter. But she throws . . . ” Allard shrugs. “Like a girl.” She uses the expression without apology.

Allard, a former all-American softball player who has coached at Harvard for 18 years, believes women can and should be taught to throw. Could she teach me? “Absolutely.”

So I went to Harvard to learn. Allard met me with a ball and two gloves, and we walked out to the softball field.

After warming up by tossing the ball back and forth at a distance of about 20 feet, we needed to test how far I could throw so we could track my improvement. I went to home plate and gave it my all. I couldn’t get the ball to first base, 60 feet away. Fifty-five was the best I could do.

Allard then gave me a straightforward lesson in the basic overhand throwing motion. It broke down Thomas’s three steps, in reverse order. I first practiced the whip of the arm and hand, then the extension backward and rotation forward, and then the step with the opposite foot. The lesson took about half an hour.

After it, we went back to home plate. Thomas had warned that simply learning the motion wouldn’t work miracles, so I didn’t expect one. And I didn’t get one. But I did get the ball to first base, and even a little beyond: That was a 10 percent improvement in just 30 minutes.

I told Allard that I’d been cautioned that instruction without practice doesn’t help much. “Neither does practice without instruction,” she said. She put a ball and a glove in my hand and sent me home.

I have been practicing. And although I’m not breaking any records, for the first time in my life, I can throw a ball with something resembling confidence. And how many girls can say that?